serial: qcom-geni: add force suspend/resume to system sleep callbacks

During system sleep the hardware resources (clocks, interconnect) are
not gated because the runtime-suspend callback is never invoked from
the system sleep path.  This prevents the platform from reaching its
lowest idle state.

The system sleep callbacks qcom_geni_serial_suspend() and
qcom_geni_serial_resume() rely solely on uart_suspend_port() /
uart_resume_port() to manage power.  uart_suspend_port() drives the
UART PM state machine to UART_PM_STATE_OFF, which in turn calls
pm_runtime_put_sync() and eventually the runtime-suspend callback.
However, if the runtime-PM usage count is still elevated at the time
of system sleep (e.g. the port is held active by an open file
descriptor), the runtime-suspend callback is never invoked and the
hardware resources (clocks, interconnect) remain enabled across
suspend, preventing the platform from reaching its lowest idle state.

Fix this by calling pm_runtime_force_suspend() at the end of
qcom_geni_serial_suspend() so that the runtime-suspend callback is
always executed regardless of the usage count, and by calling
pm_runtime_force_resume() at the start of qcom_geni_serial_resume()
to restore those resources before uart_resume_port() re-opens the
port.

Signed-off-by: Praveen Talari <[email protected]>
Link: https://patch.msgid.link/20260702-add_force_suspend_resume_to_system_sleep_callbacks-v2-1-b79e254a7015@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/tty/serial/qcom_geni_serial.c

@@ -1985,6 +1985,7 @@ static int qcom_geni_serial_suspend(struct device *dev)
 	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
 	struct uart_port *uport = &port->uport;
 	struct qcom_geni_private_data *private_data = uport->private_data;
+	int ret;
 
 	/*
 	 * This is done so we can hit the lowest possible state in suspend
@@ -1994,7 +1995,19 @@ static int qcom_geni_serial_suspend(struct device *dev)
 		geni_icc_set_tag(&port->se, QCOM_ICC_TAG_ACTIVE_ONLY);
 		geni_icc_set_bw(&port->se);
 	}
-	return uart_suspend_port(private_data->drv, uport);
+
+	ret = uart_suspend_port(private_data->drv, uport);
+	if (ret)
+		return ret;
+
+	/*
+	 * When no_console_suspend is set the console must remain active
+	 * across system sleep, so skip the force suspend path.
+	 */
+	if (!console_suspend_enabled && uart_console(uport))
+		return 0;
+
+	return pm_runtime_force_suspend(dev);
 }
 
 static int qcom_geni_serial_resume(struct device *dev)
@@ -2004,6 +2017,10 @@ static int qcom_geni_serial_resume(struct device *dev)
 	struct uart_port *uport = &port->uport;
 	struct qcom_geni_private_data *private_data = uport->private_data;
 
+	ret = pm_runtime_force_resume(dev);
+	if (ret)
+		return ret;
+
 	ret = uart_resume_port(private_data->drv, uport);
 	if (uart_console(uport)) {
 		geni_icc_set_tag(&port->se, QCOM_ICC_TAG_ALWAYS);